I've been rereading the series, and I've finally reached WH. And I've come up with a disturbing theory based on the exchange detailed in there between the Forsaken. (Specifically, the one on p. 318 in the hardback (Could be different in the paperback)).Specifically, Demandred's thoughts regarding Cyndane.

Without quotes, he thinks that she is not Lanfear but did come from the Age of Legends. If she's not Lanfear at all but did come from AoL, then she could very easily be Ilyena Sunhair herself. She would have known about the Choedan Kal like Lanfear, and she could have been weaker in the OP. (Somewhere it's mentioned that Lanfear was strong for a man or woman even in that age, so it's doubtful that Ilyena would have bested her.)

The problem with this theory is that there is very little info about Cyndane, and barely more about Ilyena (unless you count LTT screaming about killing her) I don't think the books even tell you whether or not Ilyena can even channel, which would definetly debunk this theory if she cant. Only time will tell. This theory could explain why she is called Cyndane ("Last Chance" in the old tongue). Ilyena/Cyndane is the DO's ace in the hole for the LB, and if he needs her, it's his last chance to get free. Here's how that works; in the LB, if LTT "sees" Ilyena, he'll go berserk, and hopefully (for the DO) do something stupid so that he and Rand will lose. Maybe. Possibly.